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首页> 外文期刊>International Journal of Heat and Fluid Flow >Numerical investigation of flow and combined natural-forced convection from an isothermal square cylinder in cross flow
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Numerical investigation of flow and combined natural-forced convection from an isothermal square cylinder in cross flow

机译：等温方筒横流流动及自然对流组合数值研究

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Unsteady flow and heat transfer from a horizontal isothermal square cylinder is studied numerically using a three-dimensional computational model to investigate the influence of buoyancy on the forced flow and heat transfer characteristics. The numerical model is based on a horizontal square cylinder subjected to laminar fluid flow in an unconfined channel. The governing equations in 3D form are solved using a fractional step method based on the finite difference discretization in addition to a Crank-Nicholson scheme employed to the convective and the viscous terms. Two working fluids-air (Pr = 0.7) and water (Pr = 7)-are considered, and the flow and heat transfer simulations were carried out for the Reynolds and Richardson numbers in the intervals 55 = Re = 250 and 0 = Ri = 2, respectively. The flow characteristics such as time-averaged drag/lift, rms drag/rms lift coefficients as well as Strouhal number were computed. The heat transfer from the cylinder is assessed by mean Nusselt number (and rms Nusselt number) over the total heated cylinder walls. As the buoyancy increases, the mass and the velocity of the fluid flowing underneath the cylinder increases. The fluid is injected into the near wake region with an upward motion which significantly alters the flow field in the downstream as well as upstream regions. The effects of Reynolds, Richardson and Prandtl numbers on the flow field and temperature distributions are discussed in detail. It is shown that the flow and heat transfer characteristics are influenced more for air than water. To fill the void in the literature, useful empirical correlations of practical importance are derived for pure forced and pure natural as well as mixed convection. The mixed convection correlations, in terms of the ratio of pure forced convection, are also developed, and their implications are discussed.
机译：利用三维计算模型对水平等温方筒的非稳态流动和传热进行了数值研究，以研究浮力对强制流动和传热特性的影响。数值模型基于在无限制通道中经受层流流体的水平方圆柱体。除了对流项和粘性项采用Crank-Nicholson方案外，还使用基于有限差分离散化的分数步法求解3D形式的控制方程。考虑了两种工作流体-空气（Pr = 0.7）和水（Pr = 7），并且对雷诺数和Richardson数在55 <= Re <= 250和0 < ＝ Ri ＜＝ 2。计算了诸如时间平均阻力/升力，均方根阻力/均方根升力系数以及斯特劳哈尔数的流动特性。汽缸的热传递通过总加热汽缸壁上的平均努塞尔数（和均方根努塞尔数）评估。随着浮力的增加，在圆柱体下方流动的流体的质量和速度也会增加。流体以向上运动注入到近尾流区域，这会显着改变下游区域和上游区域的流场。详细讨论了雷诺数，理查森数和普朗特数对流场和温度分布的影响。结果表明，空气的流动和传热特性比水受到的影响更大。为了填补文献中的空白，对于纯对流和纯对流以及混合对流，得出了具有实际重要性的有用经验关联。还开发了纯对流比方面的混合对流相关性，并讨论了它们的含义。

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